Myocarditis

In medicine (cardiology), myocarditis is inflammation of the myocardium,
the muscular part of the heart. It is generally due to infection (viral
or bacterial).

Epidemiology

The exact incidence of myocarditis is unknown. However, in series of
routine autopsies, 1-9% of all patients had evidence of myocardial
inflammation. In young adults, up to 20% of all cases of sudden death
are due to myocarditis.

In South America, Chagas' disease (caused by Trypanosoma cruzi) is the
main cause of myocarditis.

Causes

A large number of different causes have been identified as leading to
myocarditis:
Infectious:

Signs and symptoms

The signs and symptoms associated with myocardits are varied, and relate
either to the actual inflammation of the myocardium, or the weakness of
the heart muscle that is secondary to the inflammation. Signs and
symptoms of myocarditis include:

Sudden death (in young adults, myocarditis causes up to 20% of all cases
of sudden death)

Since myocarditis is often due to a viral illness, many patients give a
history of symptoms consistent with a recent viral infection, including
fever, joint pains, and easy fatigueability.

Myocarditis is often associated with pericarditis, and many patients
present with signs and symptoms that suggest concurrent myocarditis and
pericarditis.

Diagnosis

Myocardial inflammation can be suspected on the basis of
electrocardiographic results (ECG), elevated CRP and/or ESR and
increased IgM (serology) against viruses known to affect the myocardium.
Markers of myocardial damage (Troponin or Creatine Kinase cardiac
isoenzymes) are elevated.

The EKG findings most commonly sene in myocarditis is diffuse T wave
inversions, without shifts in the ST segment.

The gold standard is still biopsy of the myocardium, generally done in
the setting of angiography. A small tissue sample of the endocardium and
myocardium is taken, and investigated by a pathologist by light
microscopy and - if necessary - immunochemistry and special staining
methods.

Treatment

Bacterial infections are treated with antibiotics, dependant on the
nature of the pathogen and its sensitivity to antibiotics. As most viral
infections cannot be treated with directed therapy, symptomatic
treatment is the only form of therapy for those forms of myocarditis,
e.g. diuretics and/or inotropes for ventricular failure.